Re: I-D ACTION:draft-ietf-v6ops-nap-01.txt

[Mark Smith <ipng@69706e6720323030352d30312d31340a.nosense.org>]

Hi Stig,

On Mon, 25 Jul 2005 12:57:52 +0200
Stig Venaas <Stig.Venaas@uninett.no> wrote:

> On Mon, Jul 25, 2005 at 10:29:42AM +0200, Stig Venaas wrote:
> [...]
> > On Mon, Jun 27, 2005 at 06:22:17PM +0930, Mark Smith wrote:
> [...]
> > You're refering to 2.5.1 where it says
> > 
> >    For all unicast addresses, except those that start with binary value
> >    000, Interface IDs are required to be 64 bits long and to be
> >    constructed in Modified EUI-64 format.
> > 
> > I guess. I can't say I like this. I believe it's quite common in IPv6
> > to use /128 for addresses on loopback interfaces on routers and inject
> > those into IGP (just like IPv4 /32). If I understand this correctly,
> > one would then be forced to use a different /64 for each router loopback.
> > It's also pretty common to use a longer than 64 prefix for tunnels, e.g.
> > /126.
> 
> Come to think of it, is there anything preventing using the last 64 bits
> of an address as an IID when it is /126 (/128 or whatever >64)? On say a
> tunnel with /126, you would then have 64 bit IIDs that are unique to the
> link because the last 2 bits are unique to the link.
> 

I'm not sure I fully understand what you're getting at here, are you
able to expand on it a bit more ?

In some of my thinking about this host routing issue, I realised that prefix
lengths on addresses assigned to interfaces actually indicate two things
:

- what portion of the address is the node address i.e., where the
boundary between the network and node parts falls

- what destination addresses are onlink or offlink

I think it would be possible to have those two values different for a
node's interface, although IPv6 doesn't separate them at the moment. Is
that something along the lines of what you're describing with your /126
tunnel suggestion ? 

Regards,
Mark.